It may be necessary to cool motor vehicle exhaust gases circulating in an exhaust line that is connected to the engine via exhaust pipes and in which there may be arranged, for example, one or more silencers and/or one or more exhaust gas treatment devices.
In the case of an exhaust line comprising one or more treatment devices allowing the exhaust gases to be cleaned, it may be necessary to cool the circulating gases before they enter the treatment device in order that the temperature of the gases is always perfectly adapted to the operating conditions of the cleaning unit or alternatively in order to avoid destroying or damaging one or more components of the treatment device by the effect of heat.
More generally, it may be necessary to cool the exhaust gases of an engine in order to avoid damaging the elements constituting the exhaust line.
The fitting of a heat exchanger device into the exhaust line, for example upstream of an exhaust gas cleaning unit, has therefore been considered.
The most simple solution consists in the use of a single tube of great length, the conduction of the tube and the convection associated with the flow of air around the tube being used to remove energy. The disadvantage of that solution is that it may result in the use of tubes of very great length, leading to problems with installation beneath the floor of the motor vehicle.
There has not hitherto been known a heat exchanger device that is simple and compact in construction, is fitted into the exhaust line of a motor vehicle and allows the exhaust gases circulating in the exhaust line to be cooled effectively by means of air in contact with the wall of a pipe in which the exhaust gases are flowing.
In FR-A-783.570 there is described a silencer for a motor vehicle exhaust line, having a plurality of bodies, for example two bodies separated from one another by an intermediate space and each constituted by an assembly of tubes that are parallel to one another and the total cross-section of which allows throttling of the flow of exhaust gases inside the silencer. Such a device permits a certain cooling of the exhaust gases to be carried out. However, the length of the path of the gases inside each of the bodies of the silencer is limited to the length of the tubes arranged in parallel.
The object of the invention is, therefore, to propose a heat exchanger for cooling motor vehicle exhaust gases, which heat exchanger is to be fitted into an exhaust line of the vehicle, comprising at least one plurality of tubes in contact by way of their outer walls with cooling air, in which the exhaust gases are brought to circulate, comprising an outer casing of sheet metal that is substantially cylindrical in shape and through the lateral wall of which there pass openings, in which casing tubes of the plurality of tubes are fixed by holding means in substantially parallel arrangements, inside the casing, a pipe for the admission of exhaust gases into the casing of the heat exchanger, which pipe is connected to the exhaust line upstream of the heat exchanger, an exhaust gas evacuation pipe connected to the exhaust line downstream of the heat exchanger, and exhaust gas distribution means arranged inside the casing of the heat exchanger, the heat exchanger, which is simple to produce and compact in form, allowing effective cooling of the exhaust gases, the intensity of which can easily be adjusted.
To that end, the exhaust gas distribution means allowing the exhaust gases to be passed from the admission pipe to the evacuation pipe, along a path that passes in succession, in an axial direction, through each of the tubes of the plurality of tubes, along their entire length, are constituted by collectors delimited, inside the metal casing of the heat exchanger, by two axial-end cupels or outer cupels that are arranged transversely and close the axial ends of the metal casing of the heat exchanger, and by a plurality of inner cupels that are each arranged along the entire inner transverse cross-section of the metal casing, at a distance from the axial ends of the metal casing of the heat exchanger, and through each of which there passes at least one opening for the passage and fixing of a tube of the plurality of tubes, each of the tubes of the plurality of tubes being fixed at one of its ends in a first inner cupel and at its other end in a second inner cupel, each of the collectors being delimited inside the lateral wall of the metal casing by a first cupel, which may be an outer cupel or an inner cupel, and by a second cupel, which is an inner cupel.